AGE OF THE UNDERLYING ROCKS OF FLORIDA 9 J 
pecially by tyro species of Orbitolina, one a small sharply conical 
species, the other a large depressed form with usually a concave 
base. Other species are present in some of the wells, but these two 
are especially important. 
Outside these Florida wells the only region in America where 
the small sharply conical species is known is in the Quitman Moun¬ 
tains of Western Texas near the Rio Grande River about 80 miles 
southeast of El Paso. Here it characterizes a horizon of the Fred¬ 
ericksburg Series of the Lower Cretaceous and is very abundant in 
that horizon. A species which seems identical with this is found 
in the Lower Cretaceous'of the Province of Navarra in northern 
Spain on the southern slope of the Pyrenees. The specimens from 
these three remote areas, Texas, Florida and Spain, seem to be¬ 
long to one species or very closely related species. This then set¬ 
tles definitely the age of the beds in which this conical Orbitolina 
is found. 
Below the Fredericksburg in the same section in the Quitman 
Mountains, according to Stanton (in Cragin, Bull. U. S. Geol. Sur¬ 
vey, No. 266, pp. 28-32, 1905) in the Trinity group of the Lower 
Cretaceous there are horizons marked by enormous numbers of 
Orbitolina texana. This is a large, depressed form with a slightly 
concave base. The larger concave species which occurs in the 
Florida wells at some distance below the smaller conical species 
very closely resembles 0 . texana and is closely related to it if not 
identical. In Europe similar species occur in the Neocomian, 
which seems to be the equivalent of the Trinity of Texas. Other 
species occur in the Aptian beds of Switzerland where, according 
to Chapman it forms a more or less massive rock called the Orbi¬ 
tolina limestone. The Upper Greensand in Devonshire, England, 
contains a bed almost entirely made up of another species of Orbi¬ 
tolina. 
The two forms of Orbitolina would alone appear sufficient to 
define the Lower Cretaceous of these two series, but there are also 
in the Florida material other genera which in various species char¬ 
acterize the Gault and earlier Lower Cretaceous beds of Europe. 
With these groups clearly defined their distribution in the well 
samples becomes a matter of the discovery of the highest levels at 
which they appear in the well samples. 
